Cleanup QuestionDataSource and fix breadcrumb links issues (#18962)

* Remove not used `noLink` prop

* Namespace URL generators

* Fix HeaderBreadcrumbs font-size in "head" mode

* Add unit-tests for QuestionDataSource

* Allow using react nodes in breadcrumbs

* Use func declaration for QuestionDataSource

* Add prop-types

* Simplify query assignment expr

* Don't swallow errors in QuestionDataSource tests

* Add repro for #17961 (unit)

* Allow passing custom divider for HeaderBreadcrumbs

* Fix join tables breadcrumb links

* Add extra saved question utils

* Add tests for nested questions

* Fix source question link

* Don't show source question's schema

* Fix breadcrumb colors

* Fix tests

* Fix breadcrumb colors

* Use saved-questions lib utils for DataSelector